User:Jwong61/sandbox

Racemization Outline

 * add a definition and terms section - racemization, racemic mixture, racemize, racemate, d, l, R, S, briefly describe enantiomers
 * http://www.chem.ucla.edu/harding/IGOC/IGOC.html
 * G-13
 * page 78
 * discovery by Louis Pasteur of optical activity
 * page 17-18
 * thalidomide
 * page 86-87
 * other drugs such as citalopram
 * page 20
 * describe amino acid racemization
 * page 907, 910
 * Peptide Racemization
 * cataracts
 * add examples of how amino acid dating is used
 * http://www.ncdc.noaa.gov/paleo/aar.html
 * http://www.sciencedirect.com/science/article/pii/S1871101414000260
 * http://www.ncbi.nlm.nih.gov/pmc/articles/PMC433490/

Intro
In chemistry, racemization refers to the conversion of an enantiomerically pure mixture (one where only one enantiomer is present) into a mixture where more than one of the enantiomers are present. An enantiomer, also known as an optical isomer, refers to a stereoisomer of a pair of molecules that are nonsuperposable mirror images of each other. If the racemization results in a mixture where the D and L enantiomers are present in equal quantities, the resulting sample is described as racemic, a racemic mixture, or a racemate.

Discovery of Optical Activity
In 1843, Louis Pasteur discovered optical activity in paratartaric, or racemic, acid found in grape wine. He was able to separate two enantiomer crystals that rotated polarized light in opposite directions.

Thalidomide
In general, only one form of a chiral molecule will participate in biochemical reactions while the other simply does not participate or can cause side-effects. Of note, the L form of amino acids and the D form of sugars (primarily glucose) are usually the biologically reactive form. This is due to the fact that many biological molecules are chiral and thus the reactions between specific enantiomers produce pure stereoisomers.

Additionally, many psychotropic drugs show differing activity or efficacy between isomers, e.g. amphetamine is often dispensed as racemic salts while the more active dextroamphetamine is reserved for refractory cases or more severe indications; another example is methadone, of which one isomer has activity as an opioid agonist and the other as an NMDA antagonist.

Racemization of pharmaceutical drugs, however, can occur in vivo. An example is thalidomide: its (R) enantiomer is effective against morning sickness, while the (S) enantiomer is teratogenic, causing birth defects when taken in the first trimester of pregnancy. If only one enantiomer is administered to a human subject, both forms may be found later in the blood serum. The drug is therefore not considered safe for use by women of child-bearing age, and while it has other uses, its use is tightly controlled. Thalidomide can be used to treat multiple myeloma. ??? Another commonly used drug is ibuprofen which is only anti-inflammatory as one enantiomer while the other is biologically inert. Likewise, only one stereoisomer in Citalopram (Celexa), an antidepressant which inhibits serotonin reuptake, is active. The The study of enantiomers in the pharmaceutical industry is termed chiral organic synthesis.

Also notable is the fact that all amino acid residues exist in the L form. However, bacteria produce D-amino acid residues that polymerize into short polypeptides which can be found in bacterial cell walls. These polypeptides are less digestible by peptidases and are synthesized by bacterial enzymes instead of mRNA translation which would normally produce L-amino acids.

FIGURE 1– 24 Stereoisomers have different effects in humans. ( a) Two stereoisomers of carvone: ( R)- carvone ( isolated from spearmint oil) has the characteristic fragrance of spear-mint; ( S)- carvone ( from caraway seed oil) smells like caraway. ( b) Aspartame, the artifi-cial sweetener sold under the trade name NutraSweet, is easily distinguishable by taste receptors from its bitter- tasting stereoisomer, although the two differ only in the configura-tion at one of the two chiral carbon atoms. ( c) The antidepressant medication citalopram ( trade name Celexa), a selective serotonin reuptake inhibitor, is a racemic mixture of these two steroisomers, but only ( S)- citalopram has the therapeutic effect. A stereochemically pure preparation of ( S)- citalopram ( escitalopram oxalate) is sold under the trade name Lexapro. As you might predict, the effective dose of Lexapro is one- half the effective dose of Celexa.

The amino acid alanine exists only as the L-Alanine form.

Amino Acid dating []

Amino Acid edits
[Amino Acid(Common)] (abbreviated as [XXX] or [X]; encoded by the codons [codon list here]) is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated -+NH3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated –COO- form under biological conditions), and a side chain [Functional group], classifying it as a [polar/nonpolar/charged(at physiological pH), aromatic/aliphatic] amino acid. It is [essential/non-essential/semi-essential] in humans, meaning the body [cannot synthesize it and thus it must be obtained from the diet/can synthesize it/can synthesize it from the essential amino acid [another amino acid]].
 * Template

Unique/interesting info about that amino acid.

Leucine (abbreviated as Leu or L; encoded by the six codons UUA, UUG, CUU, CUC, CUA, and CUG) is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated -+NH3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated –COO- form under biological conditions), and an isobutyl side chain, classifying it as a nonpolar(at physiological pH) amino acid. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet.
 * Leucine

Leucine is a major component of the subunits in ferritin, astacin, and other 'buffer' proteins.

Leucine (abbreviated as Leu or L) is an essential, branched-chain α-amino acid, classified hydrophobic due to the isobutyl side chain. Its structural formula is HO2CCH(NH2)CH2CH(CH3)2. L-Leucine is encoded by six codons (UUA, UUG, CUU, CUC, CUA, and CUG) and is a major component of the subunits in ferritin, astacin, and other 'buffer' proteins.

Glutamine (abbreviated as Gln or Q; encoded by the codons CAA and CAG) is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated -+NH3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated –COO- form under biological conditions), and a side chain amide which replaces the side-chain hydroxyl of glutamic acid with an amine functional group, classifying it as a charge neutral, polar(at physiological pH) amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for glutamine increases and glutamine must be obtained from the diet.
 * Glutamine

In human blood, glutamine is the most abundant free amino acid, with a concentration of about 500–900 µmol/l.

Glutamine (abbreviated as Gln or Q, and often called L-glutamine) is one of the 20 amino acids encoded by the standard genetic code. It is considered conditionally essential. In human blood, glutamine is the most abundant free amino acid, with a concentration of about 500–900 µmol/l. The side-chain is an amide formed by replacing the side-chain hydroxyl of glutamic acid with an amine functional group, making it the amide of glutamic acid. Gln's codons are CAA and CAG.